Reconfigurable spectroscopy system

ABSTRACT

A reconfigurable spectroscopy system comprises tunable lasers and wavelength lockers to lock to accurate reference wavelengths. Band combiners with differently optimized wavelength ranges multiplex the optical signal over the time domain, to emit a plurality of reference wavelengths for spectroscopy applications. The power requirements are greatly reduced by multiplexing over the time domain in time slots which do not affect sampling and receiving of the spectroscopy data.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 62/528,936, filed on Jul. 5, 2017, and U.S. ProvisionalPatent Application No. 62/547,026, filed on Aug. 17, 2017, thedisclosures of both being incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present disclosure relates to spectroscopy. More particularly, itrelates to a reconfigurable spectroscopy system.

SUMMARY

In a first aspect of the disclosure, a device is described comprising: aplurality of tunable lasers generating a plurality of wavelengths; aplurality of wavelength lockers to reduce wavelength noise from theplurality of wavelengths and lock to a precise wavelength; a pluralityof band combiners each configured to combine a different wavelengthrange than other band combiners of the plurality of band combiners; aplurality of switches, each switch receiving output of a correspondingband combiner of the plurality of band combiners, each switch outputtinga plurality of switched wavelengths; a plurality of broadband combinersreceiving outputs of the plurality of switches; and a plurality ofemitters to emit a plurality of reference wavelengths, each emitterreceiving output of a corresponding broadband combiner of the pluralityof broadband combiners.

In a second aspect of the disclosure, a device is described comprising:a plurality of tunable lasers generating a plurality of wavelengths; aplurality of wavelength lockers to reduce wavelength noise from theplurality of wavelengths and lock to a precise wavelength; a pluralityof band combiners each configured to combine a different wavelengthrange than other band combiners of the plurality of band combiners; abroadband combiner receiving outputs of the plurality of band combiners;an optical phased array switch comprising at least one arrayed waveguidegrating; and a plurality of emitters to emit a plurality of referencewavelengths, each emitter receiving output of the optical phased arrayswitch.

In a third aspect of the disclosure, a device is described comprising: aplurality of tunable lasers generating a plurality of wavelengths; aplurality of wavelength lockers to reduce wavelength noise from theplurality of wavelengths and lock to a precise wavelength; a pluralityof band combiners each configured to combine a different wavelengthrange than other band combiners of the plurality of band combiners; abroadband combiner receiving outputs of the plurality of band combiners;a passive splitter configured to split an output of the broadbandcombiner; and a plurality of emitters to emit a plurality of referencewavelengths, each emitter receiving output of the passive splitter.

In a fourth aspect of the disclosure, a method comprising: generating aplurality of wavelengths by a plurality of tunable lasers; reducingwavelength noise from the plurality of wavelengths by a plurality ofwavelength lockers; combining the plurality of wavelengths intowavelength ranges by a plurality of band combiners; switching thewavelength ranges by a plurality of switches; multiplexing over a timedomain the plurality of wavelength ranges into a plurality of broadbandcombiners, each broadband combiner outputting to a corresponding emitterof a plurality of emitters; and emitting the multiplexed wavelengths bythe plurality of emitters.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of this specification, illustrate one or more embodiments of thepresent disclosure and, together with the description of exampleembodiments, serve to explain the principles and implementations of thedisclosure.

FIGS. 1-2 illustrate exemplary architectures for the spectroscopysystem.

FIG. 3 illustrates an exemplary transmitter architecture for thespectroscopy system.

FIGS. 4A and 4B illustrate two exemplary implementations for adjustingthe wavelength after the lasers.

FIG. 5 illustrates an example of operation of a wavelength locker basedon an arrayed waveguide grating (AWG).

FIG. 6 illustrates an example spectroscopy system where an AWGconfiguration with active phase shifters is used to switch (steer)wavelengths to different emitters.

FIG. 7 illustrates an example AWG-based multi-channel wavelength locker.

FIG. 8 illustrates an example implementation based on a passive splitterafter the broadband combiner.

FIG. 9 illustrates an exemplary schematic of an AWG.

DETAILED DESCRIPTION

The present disclosure describes a spectroscopy system which can bereconfigured according to the specific application. Several possiblesystem architectures are described herein.

In FIG. 1, an exemplary architecture for the spectroscopy system isdescribed. The system may comprise one or more lasers (105), each laseroperating within a different wavelength range. The wavelength ranges maybe entirely distinct, or have a degree of overlap with each other. Thelasers in FIG. 1 may be tunable. Each of the lasers (105) mayincorporate a wavelength locker (110). In some embodiments, thewavelength locker operates with a feedback circuit. The wavelengthlockers eliminate phase noise and can be implemented in different ways.The wavelength lockers can lock a wavelength into an accurate referencewavelength by controlling the wavelength variations. The lasers may becontrolled by a driver circuit which can control the laser tuning aswell as the wavelength lockers. The control circuitry may be located onthe same chip of the photonic components (e.g. the wavelength lockers)or may be located in a separate chip, e.g. a complementary oxidesemiconductor (CMOS) chip. The wavelength lockers allow a stableoperation with “clean” wavelengths. Downstream to the wavelength lockers(110), a plurality of well defined, distinct wavelengths is thereforeavailable. These different wavelengths may be combined in a plurality ofband combiners (115), followed by one or more switches (120).

The switches (120) can switch the photonic signal between differentoutput waveguides and feed each wavelength band to different emitters(125). This implementation allows the system to scan across wavelengths.For example, the switches (120) can multiplex the wavelength in thetemporal domain, by alternating over time between each wavelength. Insome embodiments, the different wavelength bands (125) can be combinedby broadband combiners (130). Each of the broadband combiners canmultiplex the wavelengths to a single waveguide that is feeding oneemitter. In some embodiments, multiplexing over the time domain iscarried out with a very small interval, e.g. of the order ofmilliseconds per wavelength. If the application does not require fastsequencing, the sample illuminated by the spectroscopy system iseffectively scanned by a plurality of wavelengths, with no perceivabledifference compared to a system that would illuminate the samplesimultaneously at each wavelength. To illuminate the sample with eachwavelength simultaneously, the overall power of the system isnecessarily split into a number of emitters. Therefore, the poweravailable, per channel, is less than that available if the wavelengthsare scanned over time. With wavelength multiplexing, the system caneffectively analyze a sample with the same number of wavelengths of asimultaneous-wavelengths system, but with greatly increased powerefficiency.

In some embodiments, each wavelength is emitted one at a time. In otherembodiments, a subset of wavelengths is emitted simultaneously, and theemitters sequence each wavelength of the subset over time, effectivelymultiplexing a varying subset of wavelengths. In yet other embodiments,both modes of operation can be applied sequentially or according to thespecific application. In the exemplary system of FIG. 1, following thebroadband combiner, the resultant multi-wavelength photonic signal isthen transmitted to a plurality of emitters (135). In some embodiments,the emitters (135) form one or more optical phased arrays.

The band combiners (115) may operate, in some embodiments, within awavelength range of about 100 nm. The 1×N switches (120) may beoptimized to operate within their respective wavelength bands ofoperation. For example, the first switch may be optimized to operate ina first wavelength band, while the second switch may be optimized tooperate in a second wavelength band different from the first wavelengthband—either entirely distinct or overlapping. In other words, each bandcombiner can be optimized to efficiently combine the wavelengthscomprised in its distinct operational wavelength range. The broadbandcombiners (130) may have an operating wavelength range of about a fewmicrometers. In this embodiment, each band combiner would receivewavelengths in its operational range from the tunable lasers.

FIG. 1 therefore illustrates an exemplary spectroscopy emitter systemutilizing a plurality of wavelength (frequency) lockers after the inputlasers, to clean the signal of phase noise, followed by a set of bandcombiners. Each band combiner combines a subset of the input lasersbased on a wavelength band (for example, 100 nm range), followed by aset of controlled switches (one per band combiner) that control whichbands go into which broadband combiner. The broadband combiners combinethe wavelength bands that are fed into them, and are followed by a setof emitters to emit light of the combined bands. The switches allowcontrolling which bands are sent to which emitters in a time-divisionmultiplexing manner. For example, the emitters can emit all bands at thesame time, and then selectively emit only a subset of bands, or a singleband, at different times. The emitters can also differentially emit thewavelength bands in the time domain through the use of the switchcontrol circuits. The control circuits can be realized in a photonicchip (e.g. silicon) or in a chip together with the CMOS controlcircuitry, with the other components. Alternatively, the photonic andCMOS chips may be separated.

In other embodiments, as illustrated in FIG. 2, a plurality of opticalchannel monitors (OCM) (205) may be used to monitor the output of theband combiners, and provide feedback control to the plurality of lasers.Therefore, in the embodiment of FIG. 1, a wavelength locker is usedright after the laser, while in the embodiment of FIG. 2, an opticalchannel monitor is used after the band combiner. Wavelength locking cantherefore be accomplished through the wavelength lockers or by usingoptical channel monitors (OCM) after each band combiner. In someembodiments, the OCMs may be combined with the broadband combiner. Inthis case, a feedback path would trace back to the lasers from theswitches instead of from the OCMs. In some embodiments, the opticalchannel monitor may require a lower number of components, compared tothe implementation with a wavelength locker. The photonic circuits maybe controlled by a separate CMOS chip, for example.

FIG. 3 illustrates an exemplary transmitter architecture for thespectroscopy system of the present disclosure. A plurality of lasers(305) generates a plurality of wavelengths λ₁-λ_(N). These wavelengthscan be combined at a switch (310) similarly as described in FIGS. 1-2.For example, laser 1 may operate in the wavelength range λ₁-λ₁₀, laser 2within λ₁₁-λ₂₀, and so on. These wavelengths may be combined so that,for example, each of the four pathways between (305) and switch (310)carries a specific wavelength range—e.g. λ₁-λ₁₀, λ₁₁-λ₂₀, λ₂₁-λ₃₀ andλ₃₁-λ₄₀. After the switch (310) the optical signals are sent to aplurality of emitters (315). In some embodiments, the switch (310) mayhave a limited optical bandwidth. In this case, not all wavelengths aresent to the same emitter at the same time, but the wavelengths arerather multiplexed over time. Therefore, the system switches wavelengthbands between emitters in the time domain to improve the link budget.

For example, emitter 1 (316) may receive range λ₁-λ₁₀ at time intervalt₁, while emitter 2 (317) may receive range λ₁₁-λ₂₀ at time interval t₁and emitter 3 (318) may receive range λ₂₁-λ₃₀ at time interval t₁.Emitter 3 may then receive range λ₁₁-λ₂₀ at time interval t₂, and rangeλ₁-λ₁₀ at time interval t₃. The switch can direct each of n wavelengthranges to the designated emitter (of n emitters), according to a timedistribution. For example, in the time interval t_(m), emitter 1 mayreceive range λ₁₁-λ₂₀, emitter 2 may receive range λ₂₁-λ₃₀, whileemitter 3 may receive range λ₃₁-λ₄₀ and emitter n may receive rangeλ₁-λ₁₀. In this way, 1×N switches can be used to improve the link budgetof the spectroscopy system by time-sharing the band power between Nemitters. Each switch can be optimized to perform efficiently within itswavelength band. In some embodiments, the switch can therefore emit anumber of pulses to each emitter. Different implementations can berealized for the sequence of wavelengths at the emitters. For example,all emitters may receive the same wavelength band in the same time slot,or each emitter may receive the same band at subsequent time slots. Forexample, each emitter may receive a different band in the same timeslot, and the same band may shift over time over the different emitters.

In some embodiments, multiple emitters might be used to increase theeffective illumination area, to cover a wide field of view, and capturea wide area of a spectroscopy sample.

In the architecture of FIG. 1, each emitter may see a different set ofwavelengths in each timeslot (including no wavelength if no signal istransmitted to the emitter for that timeslot). In some embodiments, thebroadband combiners could be optional. FIG. 3 illustrates an exemplaryarchitecture without the broadband combiners. In some embodiments, theemitters are configured to emit at all wavelengths over several timeslots. The emitters may be configured to form one or more optical phasedarrays.

FIGS. 4A and 4B illustrate two exemplary implementations for cleaning(i.e. wavelength locking) the light of the lasers: a feed-forwardcancellation method (FIG. 4A) and a feedback cancellation method (FIG.4B).

The feed-forward cancellation can comprise a phase modulator (425, PM),a phase detector (420), an optical frequency discriminator (410, OFD),and a photodiode (415, PD). In the feed-forward method, the wavelengthnoise can be designated as a Δλ deviation from the desired wavelengthλ₀. The wavelength noise from a split-off portion of the laser signal(405) is converted from the frequency domain into the intensity(amplitude) domain by a discriminator (410), the output of which is thenconverted into an electrical signal by a photodiode (415). This signalis input into a phase detector (420) which detects the frequency (phase)deviation. The phase detector, in turn, drives a phase modulator (425)to adjust the original signal (405) to remove the noise, therebyobtaining a clean wavelength (430) (i.e. equal to the desiredwavelength/frequency).

In the feedback method, a split-off portion of the noisy signal (435) isinput to a discriminator (440) and then a photodiode (445), similarly tothe feed-forward method. The phase detector (450), however, sends afeedback signal (455) to the laser. The laser can tune itself, based onthe feedback, to correct the output signal (460) to match the desiredwavelength/frequency. In some embodiments, therefore, the system mayhave a short starting time, after it is turned on, during which thelaser wavelengths are being adjusted. Other means of wavelength (orfrequency) locking are known in the art and can also be utilized. Insome embodiments, the feed-forward implementation may have a smallerwavelength range correction compared to the feedback implementation.However, the feed-forward implementation has the advantage of not havingto control the laser by itself. Implementing the appropriate lasercontrols may introduce additional complexity in the system. Thetrade-offs between the two implementations may favor one over the otherdepending on the specific embodiment of the system.

The number (m) of input lasers in the spectroscopy system can be large.For example, there can be over 100 input tunable lasers. The number ofemitters (N) can be independent of the number of input lasers (m).Likewise, the number of band combiners (P) can be independent of thenumber of emitters (N) and the number of input lasers (m). Approximatevalues given in the text and drawings are examples—other values can beutilized as understood by the person of ordinary skill in the art.

FIG. 5 illustrates the operation of an arrayed waveguide grating (AWG)wavelength locker for a system implementation comprising optical channelmonitors. Arrayed waveguide gratings (AWG) are commonly used as optical(de)multiplexers in wavelength division multiplexed (WDM) systems. Thesedevices can multiplex a large number of wavelengths into a singleoptical fiber or waveguide, thereby considerably increasing thetransmission capacity of optical networks. In an AWG, the incoming lighttraverses a free space and enters a bundle of arm waveguides. Thewaveguides have different lengths and thus apply different phase shiftsat their exit. The light then traverses another free space andinterferes at the entries of the output waveguides in such a way thateach output channel receives only light of a certain wavelength.

FIG. 5 illustrates an exemplary method to lock a wavelength. The laserlight (520), after a tap (525), is split into two wavelengths by the AWG(515). The ratio of the two electrical signals derived from the twowavelengths is monitored and kept constant. In turn, this allowseffective locking of the laser's wavelength. In FIG. 5, the outputcurrents I₁ and I₂ (505) of two photodiodes (PD) are monitored so thattheir ratio is kept constant. This implementation aims at keeping theratio between the two currents as close to 1 as possible. As aconsequence, the peaks (510) are kept at the same intensity and theoptical signal is kept centered at the target wavelength. The ratio is afunction of temperature, but the temperature dependency can be takeninto account and calibrated, for example through a lookup table or usingtemperature-independent reference devices (e.g. a thermal AWG). In otherwords, locking a wavelength removes drifts due to temperature andfabrication process variations. The temperature's fluctuations can becontrolled more easily than in other implementations, because the AWG isa passive component. In other words, the AWG does not have active powerrequirements which entail heat generation from power consumption.Therefore, it can be easier to control temperature fluctuations in anAWG as a passive component. Additionally, an AWG does not requirerecalibration, and it is scalable, in that the original signal can besplit not only in two wavelengths, but also in a plurality ofwavelengths. In some embodiments, it is also possible to implement asimilar technique without having symmetrical peaks (510).

Alternatively, the ratio between currents can be used as a wavelengthdiscriminator, converting changes in wavelength to changes in power(intensity). In FIG. 5, an exemplary AWG (515) has 1 input and 2outputs. The system of FIG. 5 can be used as an optical channel monitor(OCM) in the spectroscopy system of the present disclosure.

The AWG channel spacing and crosstalk can be designed so that thenecessary dr/dλ (e.g. dλ<5 pm) is obtained for the control loopsignal-to-noise (SNR) ratio, where r is the ratio, which is a functionof temperature and wavelength. In other embodiments, structures otherthan an AWG may be used, to provide two wavelength-dependent outputs.

FIG. 6 illustrates a spectroscopy system where an AWG configuration withactive phase shifters is used to steer wavelengths to differentemitters. A system comprising lasers, optical channel monitors and bandcombiners is illustrated (610), similarly as in FIG. 2. FIG. 6 alsoillustrates an optical phased array switch (615), comprising a switchdriver (620), phase modulators (625), AWGs (605) and a plurality ofemitters (630). There can be a performance trade-off between operationalwavelength band and power loss of the switch of FIG. 6, compared with asimple passive 1:N splitter.

In modules (605), the different wavelengths are distributed by using anAWG. In some embodiments, the beam emitted by each emitter has aconstant spatial divergence (i.e. emission angle) within the wavelengthrange used by the spectroscopy system. Therefore, in some embodiments,each emitter will emit at the same emission angle for each wavelength.In some embodiments, the 1:N AWG has arms with equal lengths. Theembodiment of FIG. 6 may not be as effective in power management as theembodiments of FIG. 1 or 2, however it may still deliver a higher powerefficiency than other systems without any switch. In FIG. 6, the activeswitch can steer all available power to one emitter at a time. If theswitch is sufficiently fast, the receivers are not affected by thetime-multiplexing of the power over the available emitters. The addedcomplexity of the switch is counteracted by the reduction in powerusage.

FIG. 7 illustrates an AWG-based multi-channel wavelength locker. In FIG.7, the optical channel monitor (705), following a band combiner (710),can demultiplex the wavelengths. A 1×N demultiplexer (720) is followedby multiple photodiodes (725), one diode per channel. FIG. 7 alsoillustrates (715) how each channel is centered at one wavelength. Insome embodiments, the optical channel monitors of FIG. 2 can beimplemented as described in FIG. 7. An example of such system isdescribed, for example, in M. Muneeb et al., Optics Express, vol. 22,no. 22, p. 27300 (2014), the disclosure of which is incorporated byreference in its entirety.

The 1×N demultiplexer (720) covers the same optical bandwidth as theband combiner (710), but has M times as many output ports and a spacingbetween the channels that is M times smaller. The demultiplexer can beintentionally designed to have large nearest-neighbor crosstalk. The AWGchannel spacing and crosstalk can be designed so that the necessarydr/dλ (e.g. dλ<5 pm) is obtained for the control loop signal-to-noise(SNR) ratio. In other embodiments, structures other than AWG may beused, to provide two wavelength-dependent outputs. The operation of theAWG is a function of temperature but this dependency can be calibratedand taken into account, for example through a lookup table. Anotheradvantage of the AWG is a reduced area requirement and reduced loss.

The technique of FIG. 7 is an expansion to multiple wavelengths of thetechnique of FIG. 5, as well as using more than two ports per channel(locked wavelength). In FIG. 5, the ratio between two currents ismonitored and kept constant in order to lock one wavelength. In FIG. 7,multiple wavelengths (channels, “ch”) are locked, to allow thecontrolled emission of multiple wavelengths for spectroscopyapplications. As illustrated in FIG. 7 (730), each channel comprises anumber of ports. The more ports used, the greater the accuracy of thelock. A plurality of reference wavelengths are kept locked. These lockedreference wavelengths are output at the emitters. This technique relieson the fact that the ratio is a more sensitive output. By havingmultiple ports in each channel (each channel corresponding to areference wavelength) it is possible to increase the locking accuracy.In other words, the accuracy in keeping the reference wavelengthconstant is increased compared to the approach of FIG. 5, where theratio of two quantities is monitored. Additionally, by decreasing thesensitivity of the reference wavelengths to parameters (such astemperature) the accuracy of the reference wavelengths is improved. Insome embodiments, the overlapping point between adjacent peaks in FIG. 5and FIG. 7 has the greatest slope and therefore the greatest sensitivityto fluctuations.

FIG. 8 illustrates an implementation based on a passive splitter (810)after the broadband combiner (806). In this embodiment, each emitter(815) receives all wavelengths. The system (805), implemented withoptical channel monitors similarly as in FIG. 2, comprises a passivesplitter (810) instead of an AWG. In this embodiment, the emitters (815)each receive all wavelengths simultaneously through the 1:N splitter(810). In FIG. 8, there is no switch, and therefore no time-domainswitching. As a consequence, a 1/N loss of power is present whencompared to a switched embodiment.

FIG. 9 illustrates an exemplary schematic of an AWG. An optical signalfrom input waveguide (903) enters a free propagation region (905), andis split into arrayed waveguides (920), followed by another freepropagation region (910). Interference within (910) allows the output(915) to provide a plurality of different wavelengths. Therefore, theAWG in FIG. 9 demultiplexer the wavelengths, splitting them into aplurality of defined wavelengths (915).

In FIG. 1, the modules controlling the wavelengths are termed wavelengthlockers, while in FIG. 2 the modules are termed OCM. However, eithertype of module may generally be termed wavelength locker in the presentdisclosure.

A number of embodiments of the disclosure have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the presentdisclosure. Accordingly, other embodiments are within the scope of thefollowing claims.

The examples set forth above are provided to those of ordinary skill inthe art as a complete disclosure and description of how to make and usethe embodiments of the disclosure, and are not intended to limit thescope of what the inventor/inventors regard as their disclosure.

Modifications of the above-described modes for carrying out the methodsand systems herein disclosed that are obvious to persons of skill in theart are intended to be within the scope of the following claims. Allpatents and publications mentioned in the specification are indicativeof the levels of skill of those skilled in the art to which thedisclosure pertains. All references cited in this disclosure areincorporated by reference to the same extent as if each reference hadbeen incorporated by reference in its entirety individually.

It is to be understood that the disclosure is not limited to particularmethods or systems, which can, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting. As used in this specification and the appended claims, thesingular forms “a,” “an,” and “the” include plural referents unless thecontent clearly dictates otherwise. The term “plurality” includes two ormore referents unless the content clearly dictates otherwise. Unlessdefined otherwise, all technical and scientific terms used herein havethe same meaning as commonly understood by one of ordinary skill in theart to which the disclosure pertains.

The references in the present application, shown in the reference listbelow, are incorporated herein by reference in their entirety.

REFERENCES

-   1. H. Abediasl and H. Hashemi, “Monolithic optical phased-array    transceiver in a standard SOI CMOS process,” Optics Express, vol.    23, no. 5, pp. 6509-6519, March 2015.-   2. S. Chung, H. Abediasl and H. Hashemi, “A 1024-element scalable    optical phased array in 180 nm SOI CMOS,” in IEEE International    Solid-State Circuits Conference (ISSCC) Digest of Technical Papers    (2017).-   3. C. V. Poulton et. al. “Optical Phased Array with Small Spot Size,    High Steering Range and Grouped Cascaded Phase Shifters.” In    Integrated Photonics Research, Silicon and Nanophotonics Optical    Society of America 2016.-   4. U.S. Pat. No. 9,476,981 “Optical phased arrays”

What is claimed is:
 1. A device comprising: a plurality of tunable lasers generating a plurality of wavelengths; a plurality of wavelength lockers to reduce wavelength noise from the plurality of wavelengths; a plurality of band combiners each configured to combine a different wavelength range than other band combiners of the plurality of band combiners; a plurality of switches, each switch receiving an output of a corresponding band combiner of the plurality of band combiners, each switch outputting a plurality of switched wavelengths; a plurality of broadband combiners receiving outputs of the plurality of switches; and a plurality of emitters to emit a plurality of reference wavelengths, each emitter receiving an output of a corresponding broadband combiner of the plurality of broadband combiners.
 2. The device of claim 1, wherein each wavelength locker of the plurality of wavelength lockers is between a tunable laser of the plurality of tunable lasers and a band combiner of the plurality of band combiners.
 3. The device of claim 1, wherein the plurality of wavelength lockers comprises a plurality of optical channel monitors located after the plurality of band combiners, and feeding back to the plurality of tunable lasers.
 4. The device of claim 1, wherein each band combiner of the plurality of band combiners is configured to operate within a wavelength range of 100 nm.
 5. The device of claim 1, wherein each wavelength locker of the plurality of wavelength lockers comprises feed-forward or feedback noise cancellation, and wavelength locking circuits.
 6. The device of claim 3, wherein each optical channel monitor of the plurality of optical channel monitor: comprises: one input configured to receive a portion of light from a tunable laser; an arrayed waveguide grating; a first photodiode outputting a first current; and a second photodiode outputting a second current; and is configured to monitor a ratio of the first current to the second current, to stabilize a target wavelength.
 7. A device comprising: a plurality of tunable lasers generating a plurality of wavelengths; a plurality of wavelength lockers to reduce wavelength noise from the plurality of wavelengths; a plurality of band combiners each configured to combine a different wavelength range than other band combiners of the plurality of band combiners; a broadband combiner receiving outputs of the plurality of band combiners; an optical phased array switch comprising at least one arrayed waveguide grating; and a plurality of emitters to emit a plurality of reference wavelengths, each emitter receiving an output of the optical phased array switch.
 8. The device of claim 7, wherein the plurality of wavelength lockers comprises a plurality of optical channel monitors located after the plurality of band combiners, and feeding back to the plurality of tunable lasers.
 9. The device of claim 8, wherein each optical channel monitor of the plurality of optical channel monitor: comprises: one input configured to receive a portion of light from a tunable laser; an arrayed waveguide grating; a first photodiode outputting a first current; and a second photodiode outputting a second current; and is configured to monitor a ratio of the first current to the second current, to stabilize a target wavelength.
 10. The device of claim 7, wherein each band combiner of the plurality of band combiners is configured to operate within a wavelength range of 100 nm.
 11. A device comprising: a plurality of tunable lasers generating a plurality of wavelengths; a plurality of wavelength lockers to reduce wavelength noise from the plurality of wavelengths; a plurality of band combiners each configured to combine a different wavelength range than other band combiners of the plurality of band combiners; a broadband combiner receiving outputs of the plurality of band combiners; a passive splitter configured to split an output of the broadband combiner; and a plurality of emitters to emit a plurality of reference wavelengths, each emitter receiving an output of the passive splitter.
 12. The device of claim 11, wherein the plurality of wavelength lockers comprises a plurality of optical channel monitors located after the plurality of band combiners, and feeding back to the plurality of tunable lasers.
 13. The device of claim 12, wherein each optical channel monitor of the plurality of optical channel monitor: comprises: one input configured to receive a portion of light from a tunable laser; an arrayed waveguide grating; a first photodiode outputting a first current; and a second photodiode outputting a second current; and is configured to monitor a ratio of the first current to the second current, to stabilize a target wavelength.
 14. The device of claim 11, wherein each band combiner of the plurality of band combiners is configured to operate within a wavelength range of 100 nm.
 15. A method comprising: generating a plurality of wavelengths by a plurality of tunable lasers; reducing wavelength noise from the plurality of wavelengths by a plurality of wavelength lockers; combining the plurality of wavelengths into wavelength ranges by a plurality of band combiners; switching the wavelength ranges by a plurality of switches; multiplexing over a time domain the plurality of wavelength ranges into a plurality of broadband combiners, each broadband combiner of the plurality of broadband combiners outputting to a corresponding emitter of a plurality of emitters; and emitting the multiplexed wavelengths by the plurality of emitters. 